For many applications, it is desirable to frequently change information appearing on large display panels. For example, at airports, at vehicle terminals and on highways, the travel conditions, and the arrival and departure times change constantly, and therefore the information appearing on display panels must be updated frequently.
By providing the display panel with an array of a large number of colored dots or indicators whose color can be selectively changed, information can be displayed on the panels by changing the color of certain dots or indicators to form numbers, or letters and words. Preferably, these dots or indicators are binary in that upon the receipt of an appropriate signal, the color of selected indicators changes from a background color (such as black) to a contrasting color (such as white) or vice versa thereby forming numbers or letters comprised of dots.
Such indicators are also useful individually to indicate a fault or malfunction condition in a device being monitored.
Although such indicators can be lights which can selectively be turned on and off, in order to minimize the power necessary to operate such indicators, binary indicators have been developed which when actuated by an electric signal generate an electromagnetic field which causes a flag or small panel to flip over. Each side of the flag is colored differently, so that when the flag flips the color displayed by the indicator changes. Examples of such binary electromagnetic indicators are disclosed in U.S. Pat. Nos. 1,191,023, 3,025,512 and 3,140,553.